leetcode_question_129 Sum Root to Leaf Numbers

Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path 1->2->3 which represents the number 123.

Find the total sum of all root-to-leaf numbers.

For example,

    1
   / \
  2   3

The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.

Return the sum = 12 + 13 = 25.

DFS:

void findPathSum(TreeNode* root, vector<int> &path, int &allsum)
    {
    	path.push_back(root->val);
		if(root->left == NULL && root->right == NULL){
			vector<int>::iterator it = path.begin();
			int tmpsum = 0;
			for(; it != path.end(); ++it)
				tmpsum = tmpsum*10 + *it;
			allsum += tmpsum;
			path.pop_back();
			return;
		}

		if(root->left)
			findPathSum(root->left,path,allsum);
		if(root->right)
			findPathSum(root->right,path,allsum);
		path.pop_back();
	}
	int sumNumbers(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int allsum = 0;
		if(root == NULL)
			return allsum;
		vector<int> path;
		findPathSum(root, path, allsum);
		return allsum;
    }